In many instances washed fabrics have undesirable properties, such as, for example, inadequate softness, low fluffiness, electrostatic charge, etc. It is often desirable to impart to the fabrics advantageous properties by treatment after washing, such as by adding liquid agents to the rinsing bath after the washing process. To be suitable for this after-treatment, these liquid agents must not only spread evenly in the cold rinsing liquor but they must also be absorbed in a short time from the liquor onto the fabrics. Suitable products are on the market which impart to fabrics desired properties, mostly softening and antistatic properties, when they are added to the last rinsing both. However, all pieces in the wash are affected uniformly by this type of treatment, which means that the laundry must be sorted before washing in view of this after-treatment. In addition, care must be taken in this method so that the after-treatment agent is put into the washing machine at the right time without direct contact with detergent.
Another disadvantage of the known after-treatment agents is that since pourability and rapid distribution in cold rinsing water are only ensured if the active substances are present in a 10 to 20-fold dilution, they can only be produced as highly diluted aqueous suspensions. This leads to relatively high costs for packing and transportation. Substances which are insoluble in cold water are unsuitable for this type of treatment, as are those substances which have no specific affinity to the fabric surface and therefore are lost with the spent rinsing water. Thus, the number of usable active substances is limited.
Use of an automatic drier saves time and space, as compared to hanging wash on a wash-line. In view of constantly increasing use of automatic driers, both commercially and in private households, there are new possibilities with regard to placing after-treatment agents into the drier and effecting the conditioning together with the drying of the wash. By after-treatment in the drier, it is possible also to control unpleasant properties of the laundry which appear only during the drying in the drier, such as an undesired damp odor of the wash, particularly when the driers are operated with ambient air, as well as electrostatic charge of the dry wash.
A number of suggestions have been made as to how to apply known and new active substances in the after-treatment in the drier. These suggestions concern substantially the use of sheet-type or compact absorbent substrates which are impregnated with active substance, and of foaming or non-foaming aerosol mixtures with which active substance is sprayed on the inner wall of the drier or on the damp laundry pieces. Furthermore, it has been proposed to use perforated hollow bodies which contain a solution or paste of active substance and which are moved in the drier together with the wash, as well as to use solid, lumpy mixtures of active substances with soluble carriers which are to be absorbed on the fabric surface during the drying process.
These forms of application have, however, a number of drawbacks. The use of solid fabric softeners results in an irregular distribution and, thus, spots on the laundry. With regard to the perforated hollow bodies filled with liquid after-treatment agents, the problem of the regular distribution of the active substances has not been solved either. Other drawbacks are the difficulties in handling these bodies and of controlling the dissemination of the active substances. When these preparations are used in spray form, undesired deposits are frequently formed on the parts of the device which are important for the operation of the drier, such as the temperature and humidity sensors. Furthermore, with regard to substrates formed of paper or woven or non-woven fabrics, the active substance adhering to the substrates, which is supposed to detach itself from the substrate and attach itself to the drying fabric, is given off incompletely and irregularly due to the fact that the substrates, which have large surface areas, stick to the wall of the drier or the laundry pieces. The preparations containing active substances on these compact substrates having large surface areas, must, in addition, be produced in expensive packages to avoid loss of volatile substances, particularly perfumes, until they are used. The loss of volatile substances during the automatic drying process is significant, just as with liquid preparations added during the rinsing process, because the preparations are added at the start of the process and then exposed during the entire drying process to the action of the hot drying air.
It has been suggested in DOS No. 23 18 596 that solutions or emulsions of after-treatment agents be sprayed into the automatic drier drum during drying, after a certain degree of dryness has been attained. This method avoids excessive losses of volatile substances; however, it has the disadvantage that, at the time of spraying, some laundry pieces are only a short distance from the nozzle and are hit by a concentrated jet of the after-treatment preparation. This leads to spots on the laundry and to irregular distribution of the active substances.
Applicants have found that these disadvantages can be overcome by spraying from a spray mechanism located at the top of the drum, as is explained more fully below.